The present invention relates to a technique for a speaker system and a speaker enclosure.
Various types of speaker systems have been developed. For example, a bass reflex speaker system or a drawn cone speaker system is a representative of such speaker systems.
“Bass reflex” is a technique for boosting bass by using Helmholtz resonance. “Drawn cone” is a technique for boosting bass by using resonance with air in the volume of an enclosure in which a speaker unit having no drive circuit is mounted.
In “bass reflex”, a small-size and slender resonance pipe is required for reducing the resonance frequency if the volume of the enclosure is small. As a result, there is a problem that the bass boosting function is reduced remarkably because air resistance becomes too high. Moreover, there is a problem that wind noise like a whistle is generated because the velocity of air passing through the resonance pipe becomes too high.
In “drawn cone”, the mass of the speaker system needs to be increased in order to reduce the resonance frequency. Although compliance of an edge supporting a vibration plate needs to be increased in order to reduce the resonance frequency, the spring characteristic and strength of the edge need to be increased in order to support the vibration plate large in mass. This contradicts the compliance. Moreover, the heavy vibration plate hardly vibrates perfectly in parallel, so that the vibration of the heavy vibration plate is apt to involve abnormal variation called “rolling” or “rocking”. The abnormal vibration brings increase in distortion and wasteful consumption of energy to thereby reduce efficiency.
For example, a technique disclosed in WO00/32010 has been proposed for making up the defect of “drawn cone”. According to the proposed technique, rolling or rocking can be prevented. The proposed technique, however, has a structure in which the weight of a vibration plate is supported by an edge provided around the vibration plate. For this reason, the edge needs to be strong, so that there is a problem that Q of vibration is reduced because of the damping effect of the edge.